THERMOCOCCUS CHITONOPHAGUS SP-NOV, A NOVEL, CHITIN-DEGRADING, HYPERTHERMOPHILLIC ARCHAEUM FROM A DEEP-SEA HYDROTHERMAL VENT ENVIRONMENT

From a hydrothermal vent site off the Mexican west coast (20 degrees 50'N, 109 degrees 06'W) at a depth of 2,600 m, a novel, hyperthermophilic, anaerobic archaeum was isolated. Cells were round to slightly irregular cocci, 1.2-2.5 pm in diameter and were motile by means of a tuft of flagella. The new isolate grew between 60 and 93 degrees C (optimum: 85 degrees C), from pH 3.5 to 9 (optimum: pH 6.7), and from 0.8 to 8% NaCl (optimum: 2%). The isolate was an obligate organotroph, using chitin, yeast extract, meat extract, and peptone for growth. Chitin was fermented to H-2, CO2, NH3, acetate, and formate. H2S was formed in the presence of sulfur. The chitinoclastic enzyme system was oxygen-stable, cell-associated, and inducible by chitin. The cell wall was composed of a surface layer of hexameric protein complexes arranged on a p6 lattice. The core lipids consisted of glycerol diphytanyl diethers and acyclic and cyclic glycerol diphytanyl tetraethers. The G+C content was 46.5 mol%. DNA/DNA hybridization and 16S rRNA sequencing indicated that the new isolate belongs to the genus Thermococcus, representing a new species, Thermococcus chitonophagus. The type strain is isolate GC74, DSM 10152.